In recent years, a pixel size has been reduced in order to realize smaller and finer solid-state image sensing devices. When an image size is reduced, however, not only a light receiving area of a photodiode as light receiving device but also a volume of a region for photoelectric conversion is reduced, and thus a light receiving efficiency lowers.
On the other hand, higher sensitivity of solid-state image sensing devices is desired in order to shoot an image with high image quality even in a state with less incident light, such as shooting a dark place or detecting a slight amount of radiation.
To the contrary, there is proposed a solid-state image sensing device using avalanche photodiodes by use of avalanche multiplication in order to achieve both downsizing and higher sensitivity (see Patent Document 1, for example).